Many-body interactions in physically adsorbed monolayers

The N-body Van der Waals interaction of a two-dimensional model rare-gas crystal made of point-harmonic oscillators is determined from the collective electronic polarization frequencies of the system. The adsorption of such a monolayer on a metallic surface produces a shift of these frequencies and of the coupled surface plasmon frequencies. The zero-point energy shift yields the total interaction energy including intra-layer and metal-induced collective effects. Numerical application to Kr physisorbed on Cu is discussed.     

Collective oscillations of the magnetic moments of a chain of spherical magnetic nanoparticles with uniaxial magnetic anisotropy

Magnetic particles moving freely in a fluid can organize dense phases (3D clusters or linear chains). We analyze the spectrum of magnetic oscillations of a chain of spherical magnetic particles taking into account the magnetic anisotropy of an individual particle for an arbitrary relation between the anisotropy energy and the energy of the dipole interaction of particles. For any relation between these energies, the spectrum contains three branches of collective oscillations: a high-frequency branch and a weakly split doublet of low-frequency branches. The frequency of the high-frequency branch is determined by a stronger interaction, while the frequencies of the low-frequency branches are determined by the weakest interaction. Accordingly, the dispersion is maximal for oscillations formed by the dipole-dipole interaction of particles, which have high frequencies in the case of a strong dipole interaction or low frequencies in the case of a strong anisotropy.     

Frequency conversion and amplification by stimulated electromagnetic shock radiation (SESR)

The coherent response of a polarizable medium to the radiation stimulated by the interaction of an incident coherent electromagnetic wave with a charged-particle beam, moving with greater than critical speed, results in intense electromagnetic radiation in the form of one or more shock fronts. The shock frequencies are shifted significantly from that of the incident wave and are tunable by parametric variation of the incident beams. The mechanism for this new effect (SESR) differs fundamentally from the laser mechanism. Production of intense quasi-coherent x-ray radiation by SESR obviates the need for x-ray mirrors and is not inhibited by the large spontaneous emission rates at these frequencies. Substantial fraction of the particle-beam energy can be converted into frequency-shifted radiation, with intensity larger than that of the incident wave, because of quadratic dependence on the interaction distance in the medium of the energy radiated into SESR, as compared to the linear dependence of Cerenkov radiative energy. Specific shock frequencies cross from below to above a given resonance frequency of the medium as the relevant two level populations become inverted. This dynamical dependence of the shock frequencies on the level populations provides the basis for new pumping and amplification mechanisms. An example of a possible SESR-based transducing-amplification system is described.     

The role of the induction zone on the detonation–turbulence linear interaction

Detonation–turbulence linear interaction analysis extends the non-reactive shock–turbulence analog by considering geometrical scaling of the noise with respect to the half-reaction distance. The analysis emphasizes the effect of structure in energizing selective frequencies, and determining acoustic amplification in the farfield. Natural frequencies are determined as eigenvalues of the inviscid non-forced interaction problem. They modify postshock energy spectra by supporting resonant amplification, and cast light on the role of the activation energy on the detonation–turbulence interaction. Detonations with higher activation energies amplify smaller scales by resonant amplification. An analysis of the bifurcation parameters reveals a strong link between detonation overdrive and acoustic attenuation. The damping is correlated with the subcritical nature of the characteristic solutions for high overdrives. For detonation conditions on the stability boundary, a larger overdrive supports a weaker resonant peak in both the temperature and longitudinal velocity spectra. Postshock temperature variances feature a well-defined maximum within the reaction zone, which is found to be sensitive to changes in detonation structure.     

Optical response of a diatomic system with allowance for the dipole-dipole interaction

The optical response of a diatomic system excited by monochromatic light is studied. On the basis of a semiclassical approach, the effects of rearrangement of the energy spectrum of the system due to the dipole-dipole interaction and the effects related to variations in the orientation of the atomic dipole moments under the action of microscopic fields are jointly taken into account. The strongest response of the system is shown to occur at dimensional resonance frequencies. The number of observed intensity peaks depends on the position of the observation point with respect to the interatomic axis. The frequencies of the dimensional resonances are compared with other characteristic frequencies of the atomic spectrum.     

Towards the proof of Kolmogorov hypotheses

A closure scheme for Kolmogorov spectrum at low and high frequencies is proposed. It allows us to validate second Kolmogorov hypothesis if expand the first one. The proposed closure scheme adds energy of turbulence to the list of controlling parameters and explains energy transfer over the spectrum by wave interaction between incompressible and adiabatic components of turbulence.     

Stepwise coupled mode scattering of ambient noise by a cylindrically symmetric seamount

The question of how underwater ambient noise, at low frequencies, interacts with seamounts is addressed. The vertical directivity of the ambient noise, with and without the seamount interaction, is of particular interest. The problem of ambient noise scattering by seamounts motivates the development of a numerical modeling procedure, based on stepwise coupled modes. The procedure is designed to analyze scattering from a cylindrically symmetric seamount. The stepwise coupled mode procedure is extended to more general boundary conditions and brought up to date in the process. An example, using the geometry of the Dickins seamount, suggests that the seamount removes energy from the steeply traveling ambient noise, for this case. The energy is not converted into angles near the horizontal; the energy is lost through bottom interaction and attenuation.     

Theory of the Magnetomechanical pole effect

The vibration frequencies of a magnetized reed can be affected by a magnetic field due to the periodic change in the interaction energy between the field and the reed. This effect was first studied by Berry and Pritchet who called it the pole effect according to a simplifying assumption made in evaluating this interaction energy. We gave here an exact first-order theory for the case of clamped-free and free-free flexural vibrations. We also give experimental evidence and the corresponding theory for a similar effect occurring with torsional vibrations.     

Interaction of longitudinal phonons with discrete breather in strained graphene

We numerically analyze the interaction of small-amplitude phonon waves with standing gap discrete breather (DB) in strained graphene. To make the system support gap DB, strain is applied to create a gap in the phonon spectrum. We only focus on the in-plane phonons and DB, so the issue is investigated under a quasi-one-dimensional setup. It is found that, for the longitudinal sound waves having frequencies below 6 THz, DB is transparent and thus no radiation of energy from DB takes place; whereas for those sound waves with higher frequencies within the acoustic (optical) phonon band, phonon is mainly transmitted (reflected) by DB, and concomitantly, DB radiates its energy when interacting with phonons. The latter case is supported by the fact that, the sum of the transmitted and reflected phonon energy densities is noticeably higher than that of the incident wave. Our results here may provide insight into energy transport in graphene when the spatially localized nonlinear vibration modes are presented.     

Dislocation theory of the energy loss during remagnetization of a ferromagnet

A general solution is found for the equation of motion of domain walls in real ferromagnets (containing dislocations) for arbitrary displacements at low frequencies of the remagnetizing field. The interaction of domain laws with dislocations is described in terms of the Peach-Koehler stochastic force. The energy loss during remagnetization due to this interaction and due to fluctuations in the domain-wall velocity is shown to depend on the dislocation structure and to be proportional to the square of the remagnetization frequency. Equations are derived to explain the temperature dependence of the energy loss during the remagnetization of transformer-steel samples varying in dislocation structure.Translated from Izvestiya VUZ. Fizika, No. 5, pp. 72–78, May, 1971.     

Softening of the LO—phonon frequencies in SmS

The zone-boundary LO—phonon frequencies of SmS show a “softening” in the semiconducting as well as in the valence-fluctuating metallic phase. This has been interpreted as a renormalization of the phonon frequencies due to the phonon-induced on-site ?-d hybridization interaction. Renormalized phonon frequencies, which are calculated as a function of the ?-d energy gap, show a larger “softening” in the semiconducting phase than in the metallic phase, being in qualitative agreement with experiment.     

Optically switched energy transfer: twin-beam off-resonance control

It is shown that, in the optical near field, the interaction of two polarized laser beams with different frequencies can promote a transfer of energy between suitably placed donor and acceptor particles, through a process that is rigorously forbidden in the absence of the laser light. The mechanism, which operates through stimulated Raman scattering by the donor-acceptor pair, is identified and characterized by quantum electrodynamical calculation. The results suggest efficiency levels comparable to conventional resonance energy transfer. Optical switching applications are envisaged.     

The rotational energy levels of four methyl groups

The energy level spectrum for a system of four interacting methyl groups belonging to an X(CH₃)₄ type molecule is calculated by numerical methods. The rotational potential at the site of each methyl group is assumed to be of a three-fold symmetry. The torsion-torsion interaction is defined as a term in the multipole expansion of the electrostatic interaction of two rigid charge distributions. It is shown, that the tunneling frequency characterizing the ground state manifold in the absence of methyl-methyl interaction, splits into a set of closely spaced frequencies.     

58Ni: an unpaired band crossing at new heights of angular momentum for rotating nuclei

High-spin states in 58Ni have been investigated by means of the fusion-evaporation reaction 28Si(32S, 2p)58Ni at 130 MeV beam energy. Discrete-energy levels are observed in 58Ni at record-breaking 42 MeV excitation energy and angular momenta in excess of 30h. The states form regular rotational bands with unprecedented high rotational frequencies. A comparison with configuration dependent cranked Nilsson-Strutinsky calculations reveals an exceptional two-band crossing scenario, the interaction strength of which is strongly shape dependent.     

Exchange-Coulomb potential energy surfaces and related physical properties for Ne-N2

An exchange-Coulomb (XC) potential energy model is developed for the Ne-N₂ interaction. The construction of this new potential energy surface is based on recent results for the Heitler-London interaction energy, the long range dispersion energies, and the microwave spectra of the dimer. The adjustable parameters in the final XC1 potential energy surface have been determined by fitting the frequencies of three representative lines of the microwave spectrum for the two isotopomers ²⁰Ne-¹⁴N₂ and ²⁰Ne-¹⁵N₂ while simultaneously maintaining agreement with the experimental second virial coefficient data obtained with the initial (unadjusted XC0 potential. With no further adjustment of parameters, the final XC potential reproduces, within 0.005%, the frequencies of the 34 microwave transitions studied experimentally for four isotopomers of Ne-N₂. Excellent agreement with experiment is obtained also for the binary diffusion, the interaction viscosity, and the mixture viscosity (for all compositions) coefficients for all temperatures. Agreement with experiment for the relaxation cross-sections associated with viscomagnetic effects, and with the pressure broadening of depolarized Rayleigh light scattering, is very good given the level of computation used for the calculations and the accuracy with which some of these cross-sections currently can be determined from experimental data. Comparisons are made with predictions calculated from the three best literature potential energy surfaces or Ne-N₂. The final XC1 potential energy surface is overall the most reliable potential energy for this van der Waals complex to date. The flexibility still inherent in this potential can be exploited, if required, in future studies of the Ne-N₂ system.     

A simulation study of microwave field effects on a 3D orthorhombic lattice of rotating dipoles: short-range potential energy variation

Variation of the short-range potential energy of interaction of nearest dipoles in a three-dimensional (3D) orthorhombic lattice exposed to microwave electric fields is studied by means of the Langevin dynamics simulations. The global increase of the mean potential energy is typical for all the frequencies and intensities at lower temperatures, whereas separate potential energy peaks or peak chains are observed at intermediate temperatures. A simple statistical model proposed to account for the temperature dependence of the field intensity for potential energy peaks suggests the concerted collective rotation of the dipoles. The temperature dependence of the peak frequency is explained using a combination of the one-dimensional Kramers and the resonant activation theories applied to the field-driven collective rotation, with the nearly degenerate angular coordinates of the dipoles being used as a single effective coordinate.     

Dynamics of inner- and outer-sphere electron transfer in a polar solvent

In this paper, inner-sphere electron transfer reactions in a solvent are studied in the framework of multidimensional transition state theory. It is demonstrated that the preexponential factor essentially depends upon the interaction with the inner-sphere vibrational mode, increasing the rate of electron transfer as much as one order of magnitude. The prefactor is shown to be strongly dependent on the frequency of this vibration. At high frequencies the rate constant increases with the reorganization energy of this inner-sphere mode while at small frequencies, electron transfer is inhibited. Estimations of inner mode reorganization energies have been performed for system where it is necessary to account nonequilibrium solvent relaxation. Finally it is shown that the equilibrium approximation fails when the reaction is close to an activationless regime.     

A model pseudopotential and energy wave number characteristics of simple metals

A model pseudopotential for electron-ion interaction in simple metals is proposed. The screened form factors of the potential are presented for 25 simple metals. Using this model potential, the energy wave number characteristics for these metals are determined. For sodium, potassium and lead, the results are compared with the numbers obtained from the analysis of experimental phonon frequencies and other theoretical calculations.     

Coherent momentum transfer due to interaction between three-level atoms and counterpropagating laser pulses

A theoretical analysis is presented of the change in the momentum of a three-level atom due to its interaction with counterpropagating laser pulses that overlap in time. The two lower energy states of the atom are metastable; i.e., a lambda-type configuration of atomic levels is considered. The cases of two and four counterpropagating pulses having different carrier frequencies are considered. In the case of adiabatic atom-field interaction, it is shown that the atom’s momentum can change by an integer multiple of the photon momentum and the corresponding standard deviation is small as compared to the photon momentum squared.     

Non-linear interaction of bending deformations of free-oscillating cylindrical shells

A method is proposed for the calculation of free oscillations of circular cylindrical shells taking into account the non-linear interaction of their bending deformations. Cases are studied in which a shell is characterized by eigenfrequencies, which are in close proximity or multiple frequencies. Based on analysis of the averaged equations, a number of solutions have been constructed. These solutions are used to investigate the particular qualities of the energy exchange and interaction of the modes of the shell. Phase patterns corresponding to interaction of conjugate forms (2-D model) and forms of various wave-forming parameters (4-D model) are studied. The impact of initial conditions on deformation shapes of free multi-mode-oscillating shells is considered.